Selective calling system



Jam 22, 1952 H. c. WATERMAN ETAL 2,583,032

SELECTIVE CALLING SYSTEM 8 Sheets-Sheet l Filed Sept. 25, 1948 RECEIVER v MV x wfz V.. my@ ME p/ VQY .H 7J c cc cc N J m E f N N m m 2 1 w r m f N Wrl i WA ww m.\

Jan. 22, 1952 Filed Sept. 25, 1948 H. C. WATERMAN ETL SELECTIVE CALLING SYSTEM 8 Sheets-Sheet 2 /lf l 2 Jam 22, 1952 H. c. WATERMAN ETAL 2,583,032

sELEcTrvE CALLING SYSTEM Filed Sept. 25, 1948 8 SheeCS--SheetI 3 Jan. zz, 1952 Filed Sept. 25, 1948 8 Sheets-SheetA 4 l Jan. 22, 1952 H. c. WATERMAN ETAL 2,583,032

SELECTIVE CALLING SYSTEM Filed Sept. 25, 1948 8 Sheets-Sheetl 5 N yN TOR5 Jan. 22, 1952 H. c. WATERMAN ETAL 2,583,032

SELECTIVE CALLING SYSTEM 8 Sheets-Shea?l 6 Filed Sept. 25, 1948 Y rolvf L/rf (TF5 ja 4142 7 425 y H. c. WATERMAN ETAL 2,583,032

SELECTIVE CALLING SYSTEM Jan. 22, 1.952

8 Sheets-Sheet 7 Filed Sept. 25, 1948 zas 4735 8 Sheets-Sheet 8 Filed sept. 25, 1948 432' fan/f FEC? SWITCH -2 /wckoP/yo/vf Patented Jan. 2 2, 1952 UNITE-D STATES PATENT Vcarrier:

SECTVE CALLING SYSTEM Herbert ,Waterman Chicago, and Marion R. Winklerf La -Grage Park, 11h,-V assi'girs Lto Motorola, Inc., PChicago, .Ill., .'afrconporatiomof Illinois -241Claims. l

"lhs 'invention yrelates `generally to vremote A'control equipmentand-moreparticularly toa selective control system `for `use with 1 communication equipment in which audioifrequency controllisig'- nais are "transmitted'fover -th'e voicecomr'nunica# tion channel.

In the zpri-or art various remote control and selective switching-equipmentf-has been developecll to provide `fastrernote control of communication equipment. The `selective `switching arrangements used in standard telephone systems i's'lan example of `suc'l'retniilzment. There-is afneeiiI for remote control systems which-may `provide vselective switching and other remote control by "the use of signals transmtiftedover v'the-regular communication channelwsothat additional channels arc'fnot required for thesc'ontrolling signals. For example, Vrit may'be desiredto -control aremote transmitter so that Vit can -be turned on- `or o and the 'frequency thereof-'selected from-a central station. -It mayalso be desired toltransmitfsignais fromV the transmitter l:for selectively call" g remote stations, such as mobile stations,` which itis desired to communica-te; To provide suchsignalling' over Athe regular communication channel would ofA course resultfin a-greatfsaving over the vuse of an auxiliarywire line or radio system for transmission of ythe control `signals.

It i's desiredthat `such remote control systems; be small and rugged `so thatthey can be used in mobile 'installations Where `v space* lis at apremium andl reliable foperation is required under relatively adverse conditions. That -is,-1the` equip ment must not be extremely 'sensitive Ato-sho'ck` or vibration `caused v'by ltheV-ehicl'e lfor t'o temper-ae' ture changes, since' thefequi-pment `vvo'nlclibe sbjected to relatively -wide temperature variations.-

To provide such va remote `vcontrolsystem, 'ivibrating vreed controlled4 Vtoner 'genera-tors andi -relh sponsive devices have beenilproduced Whie'hlarecompact and rugged 'and lviihich -providelvery ygood frequency stability fover -the requiredifoperat 1g'. conditions. In lorder to provide comp'licate`clfcori'` trol operations by they use-of"thelireedgenerators and: responders, 'switching arrangements are-rei quired so `4thatthe toneslrequired to operate `'a' particular responder can becombinediandtransmitted in "the proper sequence. The responder will react to one'iparticular combination loffrequencies to provide thef'desiredcontrol. `Such control systems must lbe flexibleso Vthat-they may be used in systems having a' large number `of stations and Where aflarge number lof different switching operations-'aire required. Thereis also' a need for such equipmentv in simple systems 55 2 wherein -a relatively ffw `c'o'ntr'ol-loperailiors =ar required. VInany iinstanceatheclierationuof the c'oritrol'simust be :sim-ple to eliminate -the need for skilled operators fand niust ybe dependable to' avoid' limproper" operation thereof l-isofar'as iis- "-It A"is ltherefore fan object fof this.im'renti-onl to provide an improved controlfsystem for"fuse-v with radioicommiincation eCi-tizio!rient.v

`A ifur'ther -o'bject-:f this inv-entiende to provide a systemorfsel'ectively combining audiofltones pairs andapply-inlg theftones over: .avoice cnam nellinaipredeterminedsequencel A= ffurther obj ect fof'this'Lir'ifvention` is: to1 provide aY controllisignal forusl inea? communication-system .forselectively calling a stationi'ri Jthe system and/or providing some other 'control functionlat airemoteis'tation.-

' -Aieature -oi tl-iis 'invention-- isl 'the Vprovisienl.of aV key loperat' switching-system l'for "combiningy certain pairs Lofa plurality 1of tones @and trans-V mitting the-same a predeterminedsequencec A fur-ther feature of this;inventionlisithe provision of la"A key operated-controlbox ori :selecting predetermined tones and a-tim'ersystemv-fo fap plyingthe A:tones- Ain a predetermined manner 'toi acommunication-channeh A still iur-ther ffeature ofmisi-invention:iis' the provision of a control system in which operation ofone svvitcliI will lpiovide'tonesw'for energizing a communication fsystemfioperationlof :additional switches will -fprovide' selective signals for calling apar-tisular stationandfreleaseof theffirst switcnf will? provide an additional signal to `disable' the communicationksystemi- Further objects; features'and' advantages Willibeapparent fromaconsideration for the f'fo1l'ow=- ing description When taken' in' 'connection "with the' accompanying drawings "in" Whidh:'

Fig; `1 iilustrates'the control systemlin'accorofance with the" invention" s'c'l'fem'ati(Zally byilo'ck diagrams ;5

Fig. 2 lis asimplified" circuitdiagani of the' control system according to the invention;

Fig. 3l isa detailedcircuit-diagram .oflthe timer' and power supply chassis ofv the-system; i

4 illustratesl vthe tone generator circuits used in'` the-system; l

lFig. wisfa `detailed#circuit diagram 'of one controlboxl-Which mayfbe'fused'; i

`Figs-611s' apenspecti-veview oflthe control' box ofFig. 5;

Figs; 7 and--areldetailediviewslillustraitingzthe mechanism: of the" controlli box fot Figs; 51'and16.;,-.

Fig. 9 is a circuit diagram of a simplified control box;

Fig. 10 is a perspective view of the control box of Fig. 9;

Fig. 11 is a circuit diagram of a modied control box; Y

Fig. 12 is a perspective view ofthe control box of Fig. 11;

Fig. 13 is a circuit diagram of a still further simplified control box; and

Fig. 14 is a perspective view of the control box of Fig. 13. A

In practicing the invention there is provided a control system for selectively applying pairs of audio tones in sequence to a communication channel for controlling equipment at remote stations. The system includes a' tone generator chassis having a plurality of oscillators# adapted to produce different tones of audio frequency. A- secon'd chassis includes timing circuits and a power supply for the entire control apparatus.'

The circuitsare arranged to apply various tones of a composite signal in a predetermined sequence. The control boxes include switching means for selectively connecting the desired oscillators to the timing circuits so that the signal transmitted includes the desired frequencies. The control boxes include facilities for transmitting tones required for various remote operations such as turning on and off a remote transmitter, or selecting certain receivers, etc. The system is also adapted to transmit signals on the communication channel which may be radiated bythe transmitter and applied to condition a particular receiver or group of receivers for operation so that communications following will be received by these receivers only. When a large number of control and/or selective calling operations are required a tone generator chassis having a large number of oscillators operating at different frequencies may be provided together with a control box which is adapted to select a large number of frequencies for the various calls.

` Onthe other hand, the equipment is suitable for use in a simple system and may then be provided with a relatively few different tone frequencies and simple control boxes for combining the tones.

Fig. 1 illustrates the remote control system in accordance with the invention as composed of threemain units, the tone generator |00, the timing circuits and power supply and the control. box |02. A standard telephone type handset |03 is shown plugged into the control box. The timing circuit may be connected to a transmitter |04 located remotely therefrom which communicates with one or more receivers |09. The operator at the control box can control the operation of the transmitter and/ or receivers and also communicate withthe operators thereat.

Fig. 2 is a circuit diagram illustrating the control system in accordance with the invention. The tone lgenerator is not shown in Fig. 2 but twelve tones of different audio frequencies provided thereby will be applied to the terminals marked Tl to T0 inclusive, T0, TA and TB. Connections are made from the terminals to one contact of each of the switches which are indicated 'as ||0I to |33 inclusive. The tone TI is applied to one contact of switches ||0 and |22, and' toneTZ is applied to switches and |23. It will be seen that there is in effect two banks of switches, one including switches ||0 to |2| inclusive, and the other including the switches |22 to |33 inclusive. Each tone is applied to one of the contacts of a switch in each bank. The second contacts of the switches in each bank are connected together and to the common leads |34 and |35 which are adapted to supply tones to the timing circuit as will be further explained. By selectively operating the-push buttons ||0 to |33, the tones applied to the leads |34 and |35 can be determined.

A plurality of auxilary switches are included I in the control box |02 including the switches |40 and |50. Switch |40 includes movable contacts |4| and |42, with themovable contact |4| being Aarranged to cooperate with fixed contacts |43 to |46 inclusive, and the movable contact |42 when the switch contact |4| is moved to the left tones T| and T1 will be applied thereto. The contact |42 is for providing operation of an auxiliary circuit of the timing circuit as will be described more in detail. Switch |50 may be identical to switch |40 and is connected so that different pairs of tones are applied to the movable contact |5| thereof. It will be apparent that when the contact |5| is moved to the right, tones T1 and T3 will be applied and when the contact is moved to the left, tones T5 and T1. The movable contact |52 provides a control connection in the same manner as contact |42.

The handset |03 is removably connected to a terminal board |55 including a terminal a connected to the push-to-talk switch |06, terminal b connected to microphone |01, and a terminal c connected to the receiver |08. The push-to-talk connection in the control box is made to the movable contact |56 of the transmit-interphone switch. When connection is made to contact |51, transmitter operation is provided and when connection is made to contact |58 interphone operation is provided as will be more fully described.

Referring now to the timing circuit |05 which is a part of the timing circuit and power supply designated as |0|, it will be apparent that various connections are made between the control box and the timing circuit. When the contact |56 is in the transmit position (engaging contact |51), and the push-to-talk switch |06 is closed, the relay |60 will be connected between plus B and ground so that the relay will be actuated. This will cause the various contacts |6I, |62, |63 and |64 of the relay to move to the left. The contact |6| is adapted to ground the terminal a on the terminal board |10 which is connected to the equipment to be controlled. This may produce some control function such as the turning on of an amplier at the transmitter. It will be apparent that this same result is produced by closing of the push-to-talk switch |06 when the transmit-interphone switch is in the interphone 65. position and contacts |56 and |58 are engaged,

7 be charged thereby, and contact-|63 `is effective to short out resistor |66. Contact |64 is effective to connect condenser |61 to the triode section |1 I, the condenser being charged from plus B before lthe relay was actuated. The voltage across condenser |61 is applied across variable resistor |68 and through resistor |69 to the grid |12 of the triode. The @anode sI'|;3 :is connected to Lplus .IB and` the .cathode 1 |14 is connected through-.relay to ground. Y When lthe .condenser '|61 is charged, .the Voltage .therefrom :applied ito :the triode :'I'II .causes the triodeatoconduct so that the .relay `I 'I5 will. be actuated.

Therelay Izincludescontacts1I'I6, |18 and |19. Contacts |T|1=andL|f|8 are-:arranged .to make connection .withrtones .TI and :and to apply .the same to :the: main @tone .conductor E |90. Contact 2|"I9 is.=;farrang'ed v.to ..short conductors IBI land |82 lwhichtare :included :invan auxiliary control circuit. Contact |116 Lcloses .a :circuit through` the relay |85'1and through theswitches I-36 and I 3T inthe control; box. As :Willi bemore fullyl explained, f the switch a |36 4.represents lcontacts which are closedfwhengany. tWoofuthefpushbuttons :I I8' to |12 I. inclusivev areuactuated. `Contact |31 similarly'represents contacts `which are closed when :any two'of l:thelpush-buttons A |722` to ISS-inclusive areoperated. yIt isi-:apparent .that when switches i |36 and I3'| vare .closed rand the relay|75 .is operated, -the relay |85 iszconnected toplus B so'thatthis'relay:Will-.be operated. `Ihe relayf|85 includes.asinglez-movablecontact |86 l.

which, when .the relayfisfactuated, yconnects the condenser I-B'i to plus B.

It Willbe apparent .thatafter a time:interval thecharge on. condenser II'Iwwill leak .oft-.through resistor L68 so Ithatthe triode I'II V-Willceasefto conduct. This Will ,permitfthe relay fII'EAto drop out so that .the contact I'It will open. This-Will of course release :relay |85 so .that .the-.contact IBS-Will .move to .the.right,:iapplying the voltage of condenser|86-toJthe-triodefsection |90. LThe condenserJis connected :across vari-able resistor |88 and through-.resistorI-892to-thegrid'-ISI vof the triode. .Theianode |92.is.connected1toplus B and the .cathode -I931is `.connected through relay wrendr switch VLI 63 to-ground. :The switch |83 willv remain .closed as. long .f as -the push-totalk switch is closed energizingrelay.I |150.

-The relay |95 includesicontacts |98;` |91 .and |98, which are moved ito .the i left -When the relay =is actuated. The contact |96 connects :the .conductor i3d to `lthefrnain 'f toneA conductor tiand thecontac-t |92 shorts the conductors -I8I-.and |92 of' the auxiiiaryicontrol system. rThercontact lconnectscondenser .|99 4-toplus .'B softhat this condenser -WilL becharged therefrom. Asiny the previous stage, i the .condenser |81 still` discharge througlrresistor I:-88after a-tinre sothatrthetriode |99 Willfcease :to conduct and the .relayV |95 will dropout. This .will cause'contact .I98-ztofmove to .thefrighttonconnect fthetcondenser |99 .to .the triode l2 89. The Voltage across-the :condenser-|199 is. appliedA across `yariable resistor 2 0 I. and-.through resistor `282 to the grid 203 of the ltriode. .The anode is connected to, lplus Band..the-.cathode connected.throughrelaylll)5 to fground.

Actuation of relayff25 causes.thelcontactsd ZilIrandfZS thereof tope-moved.tothe-dert. The contact Y. connects VAthe` conductor L|35 in the control lbox to fthe .-main tone conductor -.|80. Contact 2M shorts theconductorsl 8 I and. |92 of the auxiliary .control circuitv rand contact .208 connects the' condenser 299 to gplus.B. :After-.the condenser 4.|99 has becomedischarged vthrough resistor 2.I)I, thetrode 200 will. cease `taconduct and relay .285Willfdropoutcausing contact 288 to. move tothe-right. This appliesthe .voltage onscondenseri209 ,to ztermnal '|38 in the .control box. This Voltage .is usedtov automatically clear the lpush-button:switchfafterthe .toneszhave been trans'mittedfas Ywill `be .inorez fiullyeexplained.

When the .push-.to-lta'lk; switch |06 .iis released and =:the .relay |60 ...is thereby dea-energized, :the movabletcontact :|62 'Will..move .to the .-righteso that vthe voltage `across 'the :condenser .|65 applied-.tofthetriode 2|0. .This voltageisapplied across variable" resistor. 2| I `through :resistori2 I2 to the grid 2I3 of the triode. .Therano'deofathe triode is connected ..to,.plus. Bfandfatlfielzcathode is connectedthrough relay 2 Eatosground. .Thevvoltf age .of.condenser Ii5causesithe triode 2I0 to conduct-actuating :their-clay 2 I5'zand closing the contactsfZ I=6,=-2 I 1f fand. 2 I 8. IThe contacts Y 2 Iii-fand 2 I i are arranged to 'apply .thextones lT31: andffsto the mainrtone'conductord I 8.1and the contact -2 I 8 bridges ythe auxiliaryrconductors. I 8 I-.and I 82. :The relay 2 I 5 VWilly remain operated luntil the .condenser itt =:becomes -discharged after which ..tlie f-relay 2 I 5 wil1idropiout.

:An auxiliary "control :circuit :is @provided :for applying either .therisignal :tones or the .voice signal 4from the microphonelto'- terminali) of ethe output terminalboard I'I 0. .This circuit includes relay.` 220.7Which is energized when the conductors ISI and |162-.arezshorted- .The :conductor |'8I is connectedthroughxresistorZZI to the relay and conductor |82 .isc'onnected toplus B so'thatzthe plus -B :potential is. applied' through '.resistor `22 I to the relay -when Vthe `conductors .ft-8| A.and :|82 are fshorted. The "reiay includes contacts .222, 225i.' and 22d which lare :moved -to lthe :left when the relay is actuated. The contactx222 is n;.paral lel `with .the vcontact f IBI so that .'theiterminal .a of terminal board VI 'i0 y.remains grounded Jas llong as the relay 228 is lactuated. The .contact 223 makes connection betweenthe 'main toneiconductcr if'and theterrninal` b of terminal board "i8 'through the variable'resistor `:225. .Terminal bis usedto apply 'the 'tones ito"the1remote equipment. Contact 224 completes a-circuit `through the-.tone light |39 on the control boxand a source of voltage indicated as a battery V226. This will indicate at the control box lWh'errthe :auxiliary relay 229 isclosed.

Itwill'be notedthatwhenthe auxiliary relay 229 is not actuated, thecontactl223 connects the terminal b of 'terminalboard rIIi) to Avariable Aresistorf221. `Thisresistorfis'connectedfto the ter minal b of terminal 'board IE5-'so that the-signals from .the lmicrophone |91 are :applied `across I'resistorV 221 and through the contact 223 tothe termnal fb of terminaltboard I 18. AWhen the' relay 2.20 iv is actuated, tones f from 'resistor 22 5 'fare' applied .toi the-.terminal b. Terminalsfcfgof terminal boards |55 yand |18 are directly interconnected so that .thef receiver connection.' is completedand mayf'be extended to the remote equipment.

'Considering nov/*the operation' ofthe system in Fig. l2,V it will l'bexshoWn that the'system canhe used tol senda combination of 'tones'tota remote equipment as. foriV turning on the. transmitter iaty a remote `station, applying two sets .of tone .combinations .in= sequence Whichmaysbe transmitted by 'the remote--transmitterffor. conditioning a :ren mote receiver,'and thencomrnunicatingwith the remote -station'by useofhandset |93. .-Afterithe communication: is f finished, another combination of tones are "applied for turning :off the remote transmitter. ".Ihe tones used'for .turning geneand fl therremote rtransmitter'.'are provided by` the xed wiring in the'timinglcircuitf andv asillustrated,ith'e"'transmitter is Aturned on bytones Ti :and T3,`an'd-turned offrby tones T3rand T5. The tones for :conditioning the vremote-receiver aresset up by the: push-button switches I I 01-to- I =33 l inclusive. Although! tone combinations includingitwodifferf ent tones have been described, it is obvious that single tones can be used or combinations including more than two tones. Greater selectivity and noise protection are obtained by using a larger number of tones but this may not be necessary in certain applications and a simplied system may be entirely satisfactory.

Let us assume that switches ||2 and |20 of the first bank are actuated and switches |23.and |21 of the second bank are actuated. As Apreviously stated the switch |36 will be closed when two switches of the rst bank` are actuated and |31 is closed when two switches of the second bank are actuated. If the transmit-interphone switch |56 is in the transmit position so that contacts |56 and |51 are closed, the operator can by closing the push-to-talk switch |06 communicate directly with the receiver which is operated by the tones corresponding to the tones of the push-buttons selected. In this process the relay |60 will be closed connecting the terminal a of terminal board |10 to ground. This provides a control at the remote transmitter so that signals from terminal b of terminal board |10 are applied thereto. For example, the control may energize a line amplifier for amplifying signals applied to terminal b. The relay |60 also causes the tube |1| to conduct so that relay is immediately energized and the tones TI and T3 are applied to the main tone conductor |80 and to the resistor 225. The contacts |19 of the relay |15 energize the auxiliary circuit so that the tone from the resistor 225 is applied to the terminal b.

The relay |15 also energizes relay |85 since the switches |36 and |31 are closed. When the relays |15 and |85 drop out triode |90 is rendered conducting and the relay |95 is energized. This causes the tones T3 and TA corresponding to the switches ||2 and |20 to be applied through conductor |34 to the main tone conductor |80 and through resistor 225 to the terminal b. As the transmitter has been turned on the tones will be transmitted and may be used to provide some control operation at a remote receiver. After the relay |95 drops out the relay 205 will be energized and will be effective to apply the tones T2 and T6 corresponding to switches |23 and |21 through conductor 35 to the main tone conductor |80 and through resistor 225 and contact 223 to the terminal b of terminal board |10. This may provide the additional tones required for conditioning the remote receiver for operation so that the receiver is now turned on.

During all this time since the push-button has been depressed, the relay 220 has been actuated and the tone light |39 is illuminated. When the switching operation is completed the relay 220 will be deenergized and the tone light will be extinguished so that the operator will know that the switching is completed and he can talk to the operator at the remote receiver. The communication signals are applied to resistor 221, and as relay 220 is now deenergized, the signals are applied through contact 223 to the terminal b of terminal' board |10. When the communication is -flnished the operator releases his push-to-talk button releasing relay |50 which causes relay 2 I5 to be energized. The tones T3 and T5 are then applied to the terminal b of terminal board |10 for turning off the transmitter.

In the event that the push-to-talk switch is operated before two push-buttons are actuated in each bank, the switches |36 and |31 will not be closed and operation of relay |85 will not take Vplace in response to operation of the relay |15.

However, if the push-buttons are operated after the relay |15 has dropped out, the circuit through the switches |36 and |31 and condenser 25| will provide a current of short duration through relay |85. This will cause relay. to be actuated long enough to operate relay and then relay 205 will be operated to send out the tones in sequence as above described.

Switches are provided on the control box |02 for clearing the push-buttons or repeating the call, as may be desired. The switch 230 has three positions, a neutral position as shown, in which the push-'buttons remain in their depressed position so that the same station may be called again without resetting the buttons, a position in which the movable contacts are at the left in which the buttons are cleared after each call, and a position in which the contacts are at the right in which the call may be repeated. The switch 240 has `lust two positions, the position at the right, as shown, in which automatic clearing of the buttons may be provided, and the position in which the contacts are at the left in which the buttons may be cleared by the operator. The switches will normally .be positioned as illustrated and when the relay 205 drops out after the second pair of calling signals have been applied to the remote receiver, the condenser 209 will provide a voltage through conductor |38 which is applied through contacts 23| and 24| to the solenoid 250. The solenoid 250 works through a mechanical linkage to clear all the push-buttons. This will automatically open switches |36 and |31.

It is obvious that when the switch 240 is moved to the left the condenser 24-2, which is normally connected to plus B through movable contact 243 and resistor 244, is connected through the bridging conductor 245 to the movable contact 24| and the voltage across the condenser 242 is applied to solenoid 250 for operating the same. This permits clearing the push-buttons by the operator as desired. When the switch 230 is in the neutral position, both contacts 23| and 232 thereof are open so that no connection is made thereby. This allows the push-buttons to remain actuated so that the same call can be repeated. When the switch 230 is moved to the right, a circuit is completed through the contact 232 and through condenser 252. Condensers 25| and 252 are respectively bridged by resistors 253 and 254 to assure their discharge when not in use. With the closing of switch 230, the condenser 252 will be very quickly charged, part of its charging current tending to discharge condenser 25|, the remainder owing through relay coil |85 in an amount suicient to cause its momentary operation. This will cause subsequentioperation of the relays |95 and 205 in sequence so that the tones from conductors |34- and |35 are again applied to the main tone conductor |80 and tothe remote equipment.

The switches |40 and |50 of the control box are arranged to provide any desired auxiliary switching operations such as changing the frequency of a remote transmitter or selectively connecting receivers at the remote station. For example, the switch |40 when moved to the right applies tones T| and T5' through conductor |49 to the main tone conductor |80. The contact |42 bridges the conductors 8| and |82 of the auxiliary circuit so that the tones are applied to terminal b of terminal board |10 and from thence to the remote transmitter. These tones may control selective switches so that the transmitter will operate on a first frequency. Then whennthe.-.switchz. Mui smoved to..y the. left, the. tones TI and "ll'letare; applied andtthistnfiay.cause-4 operationvv of: ther-transmitter on. aA second frequency. Similarly, switch-1 I50-. may: be: usedto connectueither a. first. or.` a. second, receiver for4 operationV as. desired.

In 3 ,thereisshowna moredetailedcircuit diagram of the timing circuit andpovver supply. The .power supplysystem-may 'be .of anygsuitable type,. thepower supplyn illustrated.being. adapted! to; operate-from, l-lvolts alternating current` which is` appliedthroughplug 350-toa primary winding 35|... A full wave.. rectifier 3.02..is,con, nested. tothe secondary.` winding. 3.93, A,.filter. including,condensers-` 304.- and.,3.il5,;and choke 3mi.Y is .provided for smoothing. the; direct current. out.: put.. A.. pair of.y voltageregulator. tubes.. 3.5.1 and 308.- are. provided.A for.V furnishing. the, required.. voltages. Anlament.. winding- 309, provides curerent-for` heating the. cathodesofthe tubes.. Eor` applying..y power .from` thepower supply to. the.. tone. generator chassisthe. terminalsw, r, and- 1.1;l are. p rovioled v with. the, terminals. and. ...p ro, viding. heat-en. currentand.;tlr1e,terin11all ill. pro: vidingplus- Bfvoltageirom. regulator. tube. 351

The timer. chassis of. Fig... 3. providesv complete. interconnection required.. between` the.. tone` gen.- eratorand the control.boxas. illustratedgen.- orallyv in Eig..1.. 'I'he speci'c connections.r re.- quiredare shownin Fig. 3 in which theterrnnals Tl.' to. Til inclusiva. T0.I.T.A.andLTBJ. are., interconnectedwith terminals L0; 25,y 9, 268, 21;.1 and.. 28P to. .32. inclusive, respectively. The. ter minalsJto. It, inclusive and l2.to 32 inclusive at theleftside. of, E'ig 3 provide. interconnection required. between` the timer chassisand various'- oontroL boxes. The, terminali,r board Ilo` for makingconnections to.. the remote, equipment is generally similar; to that shown in .Fig 2;' but. is shownas includinga fourth terminal d;' which provides a common connection which may be usedto provide additional controls .or'as a groundconnection, An additional terminal board 3,20" is provided. for connecting a; handset, intoV the timer chassis if' desired.

In F,ig .3 therois illustrateda pair OTterminal's 32|. and 322 to which a f oot switch may bev oo nnected for, use instead of 'the push-to-talkpswitch on handset or microphone, if desired; Fig, 3'

also illustrates an amplier 323, Whicli may be l resistor 225 may be applied to the grid-,324-L of a double triode tube* 325" andaiter two stages of' amplication in the' two sections of the doubley triode, thev tones are applied to the cathode follower 3251. The ampliii'ed signa-ls' are derived from the cathodefollower'by transformerwinding 327. ,The seconcl'ary windingl 323" of the transformer is connected to the main terminal" board'3l5 lof-.the time chassis. Interconnection can.A be made, throughV terminal boardv to the contact 223 of11elay-220; sot-hat theafmplijedtone signals are applied to terminal b of.` the output; termina-lboardV lli' The main; terminal board 3l 5"- permitsvarious interconnections of the*r timer circuitL and connectonsbetweenthe timer circuits andltlfie'cone1 trollboxes, 'I lie connections illustrated provide: operation assdescribedfin, connectionwith :t and. are. proper4 for operation.:V with the. controll box-...illustrated in..Eigs...5,to-. 8. it.. will.. be.A obvious. that for: usein. other systems,v various .other com nectonsrof thefmain terminalboard 3 I5 may begffreqllired. In, other respects. the system ofn Rigas isidenticalito that of Fig.,2 and consequently willv not; befdescribed. The same ref;- erence,` numbers.: arey used to; identify the corresponding.; components in` eachcasev to simplify study of-.thecircuit In. .Eigi. il there. is, :illustrated the constructionof' theotoner generatore- As. shown inFig. 1', the tone generator is." adapted` to beinterconnected with the chassis; including the. timing circuits and power supply.v (Fig. 3) and power connec tions-aref made tof the. tonefgeneratorthrough ther-terminals and yg. The tonesv producedk by: the-...generator a-refsupplied to: the` timing chassis through-- terminals TI; to- T9 inclusive; '11033, TA. and1TB5. The oscillator circ-uitfor tone TL- is, illustrated in detail. and' thel oscillator for the-f other-f circuits` willben of r generally similarV construction.f Vibrating-A reed -structures are used fory'determining the frequenciesY of the oscillators; of; the/toneJ generators in` thel mannen described? in. thev copendingfapplication` of Marion Rf. Winkler? SePiaLNO. 343, filed January- 2, 1948, now Patent-f No-. 25475027., subject: Vibrating Reed.. Gontrolledv Oscillator.y They circuit dis*- closedfis'fslightly; different: thanthat ofY the apiplicationt referred, to but operates; generallvin accordance: with; the same-. principles.

The oscillator forv tonee'I-J includes. a vacuum tubef350; having a triodesection-and" two diode sections.` Thetplate i 35iT of? theV triodeis con'-V neoted;through-fresistor 352 tosthe-p1us B poten- -Y tial supplied from' terminall Winding 353 is^ i coupled'I to:v thef plate; 351. through condenserf 354 and antap onitloe resistorxl 352. Asecondwinding- 35.531 isfcoupled. to the grid355sof; the tube'by condenser 351.' Bias for the-grid is providedy by resistors 358. and 3.59,V the common' terminal of' which,` isf-cenneotedtofthe.anodes of the diodesv includedsin,thertub e1355. A feed-back condenserf 360: is provided.- between` the= plate 35|` and the-.anodesfofz the diodes. Vibrating magnatie. reeds 35|: ands, 352 arepositioned within the. coils; 3.53.Y and.A 355i and aref mounted on a commons.support.363- Magnets'365 .provide fixed magnetic eldst. about. the reeds; AsA fullyY de. scribed in: theappl-icationreferredto, the vi-4 bratinggg reeds together with *the coils.4 form a.

sharp filter..rv permitting4 feed-back at. onepar.

tisularv frequencyonly. 'Bhe diodesprovide am. pliiieel automaticl volumecontrol so that the amplitude: of; oscillations-- isgrestricted tothereby. increase the frequency stability.` To, providetonesaof different frequencies; thelengths and therequiredY tones. 'of differentY frequencies;

Figs: 5ito-8inclusivevillustrate more in` detail the; construction of ajcontrol box for use, in theselectivez remoter control system. This control bois; provides; ai veri@A large number ofV diierentselective@ calling. combinations and., remote con-.-` troli operations; The operationsprevouslv des` soribedaimconnection .with Fig. 21 canine-produced by;this;sont rolbox aswell as othercontrol furlo-v tions. whichlwill; beapparent, from. the iollowing.

description. 5.. illustrates .tliecircuit of theY control box which includes a connecting plug 400 having a plurality of contacts with the contacts |vto` l inclusive and l2 to 32 inclusive engaging the similarly numbered contacts of the timing circuit and power supply chassis as illustrated in Fig. 3. The control box includes push-button switches ||0 to |33 inclusive for selectively connecting the various audio tones to the timing circuit. As vpreviously described, the' push-buttons are in two banks with the first bank including switches l|0 to |2| inclusive and the second bank including switches |22 to |33 inclusive. The 12 tones from the tone generator are connected to the 12 switches in each bank with the tones being applied through contacts 1 to |0 inclusive and 25 to 32 inclusive. K

As illustrated in Fig. 5, each push-button switch includes a plurality of contacts indicated as e, f, g and h. The contacts e of the individual switches are arranged to connect the individual tones to the conductors |34 and |35 of the two banks. Resistors 40| are provided for isolating the various tone oscillators from each other, and connections from the tone generator to the conductors |34 and |35, which connect with the timing circuit, are made through the resistors 40|. The movable contacts f, y and h of the individual switches and the iixed contacts associated therewith, are for the purpose of providing the connections schematically represented by switches |35v and |31 in Fig. 2. As previously stated, a continuous series circuit is provided when two switches in each bank are operated. This series circuit extends from point 402 to point 403 of Fig. 5. Assuming that switches 2 and |20 of the rst bank are actuated as in the previous example, it will be evident that the contact h of the switch 2 extends the connection from point 402 to the row of contacts normally associated with the contact members g. Operation of the switch |20 will provide a continuous path from the row of contacts normally associated with movable contacts g through the particular contact g of switch |20 to the row of contacts normally associated with movable contacts f. This will provide a continuous circuit to the point 404. The second bank of switches will operate in a similar manner to continue the connection through the contact h of switch |23 and the contact g of switch |21 to the point` 403 which is connected through terminal |9 and which makes. connection within the timing chassis to plus B for energizing the relay |85 as previously described.

The switches |40, |50, 230 and 240 operate in exactly the same way as described in Fig. 2. The switches are illustrated in a differentmanner in Fig. 5 but the function is exactly the same. In Fig. 5, the switch construction shown isthe same as that actually used in a model as illustrated in Fig. 6.

Figs. '7 and 8 illustrate the locking and release mechanism of the push-buttons. `In Fig. 8 the button ||4 is shown depressed and being held in depressed condition by latch bar 405. Springs 406 tend to restore the buttons to normal position and springs 401 urge the latch bars 405 in engaging position. A releasing mechanism including the pivoted levers 408 engage the latch bars 405 to move the same for releasing'the push-buttons. A common arm connects with the various levers 408 and is connected to a solenoid 250 through a linkage 409. It is'therefore seenthat when the solenoid is energized the levers'are all pivoted to release the four latch bars of the four l2 rows of contacts and thereby simultaneously release all the push-button switches.

Figs. 9 and 10 illustrate a control box for use in a much simpler selective calling system. Fig. 9 is a wiring diagram of the control box and Fig. 10 shows the appearance of the box. This system is adapted to be used with the timing circuit and power supply of Fig. 3 and with a tone generator which provides only four different tones. The connections are made to the timing circuit through terminals 2, 3, 6 to |0 inclusive, |3 to I6 inclusive, I8 to 22 inclusive and 24. These numbers correspond to the numbers shown on Fig. 3 and therefore show the connection of the control box to the timing circuit. The four tones used are applied to the terminals 1, 8, 9 and |0 and from these terminals are connected to the contacts of the calling switches 4|0, 4|| and 4|2. Each of the calling switches includes a movable contact 4| 3 adapted to interconnect the fixed contacts 4|4 and 4|5 to the first tone conductor 4|6 and a. second movable contact 4|1 adapted to connect the fixed contacts 4|8 and 4|9 to the second tone conductor 420. The xed contacts 4| 4, 4|5, 4|8 and 4|9 are connected through resistors 421 to the terminals to which the tones are applied and the switches are therefore effective to apply the tones in pairs to the tone conductors. The Switch 4|0 includes a third movable contact 42| for interconnecting conductors 422 and 423 which are connected to the terminals I9 and 20. This provides a connection for energizing relay which in turn causes energization of relays and 2.05 in sequence for applying the tones from conductors 4|0 and 420 in sequence to the resistor 225 and then in the usual manner to the output terminal board. The condenser 25| and resistor 253 are provided between terminals 20 and 2| and function as in Fig. 2 to cause momentary actuation of relay |85 in the event that the selective switch is operated after the push-to-talk switch has been depressed.

A microphone may be connected to the receptacle 426 which provides connections to the timingcircuit and to the output terminal board in the manner previously described. The control box includes a, transmit-interphone switch 424 which operates in the manner previously described and a tone light 425 which indicates to the operator when the control operations are completed. It is therefore seen that by operation of a single key the operator can transmit the desired tone combinations for calling any one of three different units. The operator can then communicate directly with the selected unit. It is obvious that more than three keys can be provided in such a unit if it is desired to call any one of a larger number of remote stations. In a larger system a tone generator providing a larger number of different frequencies can be used to provide a large number of different calls.

Figs. 11 and 12 illustrate a control box for use in the system for providing a plurality of remote functions, each of which is controlled by two tones. This control box includes only terminals 4,5, 1 to I0 inclusive, |2 and I'B to I8 inclusive. These terminals are adapted to interconnect with the corresponding terminals on the timer circuit illustrated in Fig. 3. The control box includes three switches 430, 440 and 450, each including' three double throw' movable contacts. v"Ihe switch 430 includes xed contacts 43| and 432 connected to the tones applied on terminals l0 and 9 respectively. These tones are connected through the movable contacts 433 and 434 to the tonefconductorf 46 0T which is connected. to termite nal'.` L and"n applied L to f. theztimingcircuit: When the switchiis inxthe'` other position, thermovable contacts:Y 43$ and 434- engagegixed contacts- 435 and" 4'36-'and connect the. tones applied to terminal's'fand Sito the toneconductorwllrll; Switch 43th includes ai. movable. Contact `llllA adapted tor engage contact 438501" fanytime theiswitchjs operatedto short the conductors'46l and 462-and thereby operate the auxiliary relay 220. so that the tonesV are applied tothe. output' terminal roardlv The switches .44H` and 4505maylbe'identical` to theswitch 430 andiused'torproduceiadditionai' control functions.-

Each of the'switches`v430; 440 and45|l function insubstantially` the same: manner' as.. switches" Mill-and` |50 of'F'ig; 2 and'zmay"b-efused"in one position to I.turn on equipment .and in theother: position. to `turn ther equipment off. A largerrnum'- ber off switches 1 may'.v obviouslybe provided in` a large/rs controi boxfforfproducing :a larger'numberr of? switching functions. In; this case more than four.` separate audiotones. mayfbe requiredi' As illustrated in4 Fig; 112l indicating. means 4-1 il." may 1 be provided to indicate the last 'position in which the switches have-been moved 'so-'thatthe operator can tell the condition*- of the'- remote equipment.l Such means may also be provided for the switeheson theothercont'rol boxesde scribed as the switches are operated momentarily to send'- pulses '1 which providecontinuous operations. Means for indicating the 4lastt position of: the switches-S` and therefore thev condition off' the equipmentmay be of'very great value1.4 Eorindieating theposition; of these-switchesfat'a remote point auxiliary switches..IWIv 412- andl4'13- (Fig. 1'11) are provided' which may be-mechanically-in ter-connected with the'eswitches.: 439V; 44D i and 415%' respectively; Theltermina'l strip 4T# may bei pro"- videdV` forf interconnection frwauxiliary switchesv 412-, del?,v and 414 withk remoteindicating means' suc-h as a panel of' lights. (Lonnections'madeb'e-V twen theterminals to 6e of theterminal stripV and terminal 'l through suitable`- indicating means` will `energizethe lmeans when theswitches are-operated.- Thecontrolbox ofl'ig.l l2J also inciudes the tone' light: 415*- whichv4 indicatesA when the switching-operations .arev complete.

InFigs. 13l and 14' there is"illustratedaI very simple control box in which one remote-station can be called. Thecontroi'box includes asingle calling key 48s, the usuali' transmit#interphone switch 48|; tone light 482; and' a handset; receptacle 483-. The terminals of' the'control boxA arel numbered tocorrespond with the' terminals of the timing' circuit of `Fig. 3f and it'willbe'ap parent that' when thef-push-toetalk"switch isoperated, the timing' circuit' willvoperate" in the marnner.Y previously describedi The` four tones aref-providedfintlieboxf'through' terminals T; B; 9* and Iii and connection is' made. to'V theetiming circuitT through terminals 22 and 241' When the key LlSll'is moved`tbnthezcallLandLtalk position; the" movable contactY x85 functionsft'crl g1ound="tl1e ter= mina'l a of `the connector`483`f This'swit'cli therefore provides the functicml previouslydescribed'` as preformed by theA push-toetalk switch` and therefore such a switch need not be used. Thisl switch operates to'actuate relayf |60 of'f'tlieltiming circuit which; in turnY operates relayf |153 to'fsend theV tones for'turningtoni the..transmitter. l The contact" 486; connects? conductors |95. and: 2.0. to:

energizetherelayfl 8.5 sotthattheeselectiyecallingr tones are:4 applied in` sequence; Condenser." 2.51,; and: resiston 253 areeprovidedv for momentarily1 14 actuating. the; relay |85 in; the event: thatV the; controlboxis usedv in a system inf which it is not.

desired tor-use -tones for the purpose ofv turning;

the: transmitter: on andoi. The connectionfor turningion the transmitter is; made when the key 4% is moved to either the. call-and-talk o1'. the talk only position, so that. communication canbe; carried on either when thev connection hasjustv been made or` at any subsequent. time. In the talkV onlyposition, no connection .is made between'terminals 9 and 20 so that the relay |85 doesnot operate to send out the selective tones'. The single key control box may be used when several units operate from the same transmitter as a plurality ofv different taxi cab companies.

The. dispatcher foreach company will..have"a singlelkey; box for callingthe cabs of his com.- pany when he desires.

Itisseenfromthe. above that there is pro.v

vided; a remoteA selective calling and selectivey switching; system. which is applicable` for: use in. systems; which are relatively; large and, complicatedand also `for systems. which. aresimple and include only a fewstations. The system using. thefcontrol. box illustrated in Fig. 5.. can have more than two thousand different calls. The systemprovides very rapid control and/or selection of oneV or more remote stations. The system is exible in operation and the various remote controlling operations provided may or maynot be used directly with a communication sys-.1 tem. It` is obvious that other controls necessary or desirable l in a system which might be required. by; police or fire departments for example,

maybe provided. Operation ofthe system is very simple-so that a dispatchermay quickly call the desiredremote stations andtransmit a message thereto and a special switching or control operator. is. not required.

Although several specific. embodiments.. of the illustration have been illustrated, it is obvious that various changes and modications can be made without departing from the. intendedsoope of theinvention. For example, control boxes including various features of the control boxes illustratedin agreat number of` different com'- binations can be provided.. It is'therefore desired that.V therinvention be limited only to the extent dened in the impending claims.

We. claim:

1..In a selective calling system for operating remote equipment in. response to predetermined tones a sourcel of a. plurality of` tone signals,V timingl means, and push-button controlled switching. means .for selecting a plurality of pairs` of said tone signals, and. for applying the samevv box. including locking push-button switches adapted'tc be operated inV any sequence to select a plurality of pairs of said tones,` and timing means for transmitting said pairs of tones in a particular sequence, said' control box` including means for releasing` the push-buttons which have beenv operated when the selected tones have been transmitted;

Elgin a selective callingA system for operating remote. equipment `in response to vprecreterniined" toneathe combination comprising a pluraiityfiof continuously.. operating. tone generators.v for pro` box including push-button controlled switching means for selecting a plurality of pairs of tones, and timing means connected to said control box for transmitting said pairs of tones in sequence, said control box including means for causing operation of said timing means to repeat the transmission of said tones.

v- 4. In a selective calling system for operating remote equipment in response to predetermined tones, the combination comprising a plurality of continuously operating tone generators for producing tones of diierent frequencies, switching means rior selecting said predetermined tones, and timing means for transmitting said predetermined tones in a particular sequence.

5. In a selective calling system for operating remote equipment in response to predetermined tones, means ior continuously producing a plurality of tones, switching means, for selecting said predetermined tones in any order, and timing means for transmitting said predetermined tones as a plurality of pairs applied in sequence.

6. A remote control system for use over an audio channel which carries communication sig-- nals, comprising a source of a plurality of tone signals of different audio frequencies, and control means for selecting certain ones of said tone signals and applying the same to said audio channel, said control means including circuit means for automatically disconnecting said communication signals from said audio channel while said tone signalsV are being transmitted thereby.

7. A remote control system for use with communication equipment and adapted to provide control signals over the audio channel which carries the normal communication signals, comprising means for continuously producing a plurality of tone signals of different audio frequencies and a control box including switches for selecting certain ones of said tone signals and applying the same to said audio channel, said control box including circuit meansk controlled by said switches for disconnecting said communicating signals from said audio channel while said tone signals ar-e being transmitted thereacross.

8. Control equipment for providing remote selective control of communication equipment and communication therewith over a single audio channel comprising a source of a plurality of tone signals or" diierent audio frequencies, a microphone having a push-to-talk switch included therewith, a circuit connected to said source of tone signals and said microphone including means for automatically applying at least one of said tone signals to said channel in response to operation of said switch, a control box including push-button switches operable for selecting additional tone signals, said control box including means for applying said additional tone signals to said channel. after said rst tone sig-nal and means for thereafter connectingsaid mi- .crophone to said channel, and release means for automatically restoring said push-button switches after said additional tonesignals have tion of said control means, means for selecting additional pairs of tone signals, said control circuit including means or applying said additional pairs of tone signals to said channel insequence after said rst pair of tone signals and means for thereafter connecting said microphone to said channel, said control circuit including means for applying a further pair of tone signals to said equipment when said control means is released. v

10. Control equipment for providing remote selective control of communication equipment and communication therewith over a single audio channel, comprising a source of a plurality of tone signals of different audio frequencies, a microphone, a switch, a circuit connected to said source of tone signals, said microphone and said switch, and including first contact means automatically operated for applying a first pair of said tone signals to said channel in response to operation Vof said switch, means for selecting additional pairs of tone signals, said control circuit including second contact means for applying said additional pairs of tone signals to said channel in sequence after said first pair of tone signals, third Contact means for thereafter connecting said microphone to said channel, and fourth contact means for applying a further pair of tone signals to said equipment when said switch is released.

11. Control equipment for providing remote selective control of communication equipment and communication therewith over a single audio channel, comprising a source of a plurality of tone signals of different audio frequencies, a microphone having a push-to-talk switch ineluded therewith, a circuit connected to said source of tone signals and said microphone including means for automatically applying a first pair of said tone signals to said channel in response to operation of said switch, means for selecting additional pairs of tone signals, said control circuit including means for applying said additional pairs of tone signals to said channel in sequence after said first pair of tone signals and for thereafter connecting said microphone to said channel, said control circuit including additional means for applying a further pair ot tone signals to said equipment when said switch is released.

12. Control equipment for providing remote selective control of communication equipment and voice communication therewith over a single audio channel comprising tone generator means for continuously producing a plurality of tones of different audio frequencies, a microphone having a push-to-talk switch included therewith, a circuit connected to said tone generator means and said microphone including means for automatically applying at least oneof said tones to said channel in response to operation of said switch, means for'selecting additional tones, said control circuit including meansfor applying said additional tones to said channel after said rst tone and for thereafter connecting said microphone to said channel, and means for indicating when said microphone is connected to said audio channel.

13. vControl equipment for providing remote selective control of communication equipment and voice communication therewith over a single audio channel comprising tone generator means for continuously producing a plurality of tones of ldiiierent audio frequencies,'a microphone having av push-to-talk switch included therewith. a.

is Saidiieee, generate recensie controlaba to which s "ad tones-fare*applidl'including means forse- 17;- circuit connected to 1s*aidt`or,i,e,g and,` said microphone including matically applyinga least fn' said. channelfinr res o n i switch,meansv for select control circuit includingpmeansfor ap ying sa additioiial tonesy tfsaid h tone Aand for tnereaft phone to said audi'oflia' nei.

'14,'A systemro'r cp a remote station and ff ing and` communication sig mitter' for transmission the Kb source of a pli'ina'lity'1'of` dii'e timing' circuitconnegted Signals, acontroibox' o whi t are'applied, a micropnonehay g con connected tosaidfcdii bo includingimeans for. p cuit, signals from said n trolmeans and selectedfpair said timing circuitinlclud gfm dierenttones of raudio Yfrequency; "a1 iruit connected to said source y"of tones;` 1"'b0'X to'which said, tonesV7 are' applied, a mic plnone having controln'caiishonne edto'" sa" ontrolnox, s'adcontroi boxincludingjnie'ans nnecting said microphone andsel'ected pairs' after. said second'oerat 'forA microphone tofsid trans' .liters th ai es e can 'be transmitted ther'ebnjand our' acts'j operating `in` response'to elease 1 of` aid tonesto said Ytiming circuit; s'ai'd means for applyingfan additio ,c including contactmeans operating jin" nals to said transmitter fo 'se'ue ce in'response Atoa signal froirrsaidcorif-A l-J ,"g'" l v. J-

'15. A sy trol bOX ifiwhieheid wees are, i, phone 'having control"meanscoiinected i control bois, Said controlen including meansffor" rophone and said control"`means andselected airs of said tones to said timingv circuit, Said timing circuit including Contact means actuated'in" response to a sigstein f or controlling a communication, 'c l'u'ding) a plura'lityjof remote" stations" ak central s'tation' and" inwnicn av 'single' ch c prclivides` botti control* and' coin-' '911,' cdmnlisne tone generatorlnn fOr nal from said control meansf'orapplyingto'sajid 5.5:@ Q q i ncy, a timing circuit transmitter in sequence; a rst'pairoftonesior' nected to 'saisdur or tones, a conti-'o1 box to" turning Said transmitter. 01,1 Seid, Peil@ 9i Selected w ,said tones areappueu iiiciudingmeans" for' tones for transmission to'said reciyers for selec,- tively rendering said receivers' operative, a signals from said microphoiie'if .69; said selected receiver, said ti ing :further contact means f applying t 0f 'I'SI' ff leaving comme@ iefseie .weird bos. ,Seid "i @0X Der?? letare@Hillel??e91.ifiiheioltimingV a 't ,fari @nineties Seid mierorhfene, and, sanivr i 1 l Q and im? applying saidase.- if control means a '65 including contact means automatically operating 16. A system for controlling from a central staglgtrsqlrlrn nfl respollsfe totopelatlon df tiona communication network including atransh o ea'ns or ppymg o Saud au .lo mitter at a rst remote station and a plurality of c annel m sequence a mut pau' of tones and Sald receivers at other remote stations which are renslected pairs of tones for providing control func' dered operative in response to tones of particular 70 no ns' an@ for Connecting Said microphone t0 frequencies and in which system a Single audio said audio channel for communication therechannel is used for Com-,T01 and communication over, said timing circuit including additional concomprising tone generator means for continutact means for applying an additional pail 0f @ugly producing a plurality of different tones of tones to said communication channel when said audio frequency, a timing circuit connected to 7 5 control meansisreleased.

19. A system for controlling a communication network including a plurality of remote stations from a central station, and in which a single audio channel provides both control and communication, comprising tone generator means for continuously producing a plurality of different tones of audio frequency, a timing circuit connected to said source of tones, a control box to which said tones are applied including means for selecting pairs of tones, a microphone having control means connected to said control box, means interconnecting said control box and said timing circuit for applying signals from said microphone and said control means, and said selected pairs of tones to said timing means, said timing circuit including contact means automatically operating in timed sequence in response to operation of said control means for applying to said audio channel in sequence a rst pair of tones and said selected pairs of tones for providing control functions, and for connecting said microphone to said audio channel for communication thereover, said timing circuit including contact means actuated when said control means is released for applying an additional pair of tones to said communication channel, said control box and said timing circuit including provisions for applying other pairs of said tones to said audio channel independently of operation of said control means.

20. A system for controlling a communication network including a plurality of remote stations from a central station, and in which a single audio channel provides both control and communication, comprising tone generator means forv continuously producing a plurality of different tones of audio frequency, a timing circuit connected to said source of tones, a control box to which said tones are applied for selecting pairs of tones, a microphone' and a switch connected to said control box, means interconnecting said control box and said timing circuit for connecting said microphone, said switch, and selected pairs of said tones to said timing means, said timing circuit including contact means operating automatically in response to operation of said switch for applying to said audio channel in sequence a rst pair of tones and said selected pairs of tones for providing control functions and for connecting said microphone to said audio channel for communication thereover, said control box including indicating means for indicating when said microphone is connected to said audio channel, said timing circuit including additional contact means for applying an additionalv pair of tones to said communication channel when said switch is released.

21. A system for controlling a communication network including a plurality of remote stations from a central station, and in which a single audio channel provides both control and'communication, comprising tone generator means forA continuously producing a. plurality of diierent tones of audio frequency, a timing circuit connected to said source of tones, a control box to which said tones are applied for selecting certain of said tones, a microphone having a pushto-talk switch connected to said control box, means interconnecting said control box and said timing circuit for connecting said microphone, said push-to-talk switch, and said selected tones thereto, said timing circuit including contact means operating in response to operation of said push-to-talk switch for connecting to said audio channel in sequence, at least one tone for providing a rst control function, said selected tones for providing a second control function, and said microphone for communication over said audio channel, said timing circuit including additional contact means for connecting at least one additional tone to said communication channel when said control means is released for providing an additional control function.

22. :In a selective calling system for operating remote equipment in response to predetermined combinations of signals, a source of a plurality of electrical signals of diierent frequencies, timing means, and push-button controlled switching means for selectively applying a plurality of cornbinations of said signals to said timing means, said timing means transmitting said combinations of signals in sequence.

23. In a selective calling system for operating remote equipment in response to calling signals each including a plurality of tone signals, tone generator means for continuously producing a large number of dierent tone signals of audio frequency, a control box including means for combining predetermined ones of said tone signals for producing diierent calling signals, and timing'means for transmitting said calling sign'als in a predetermined manner.

24. A selective calling system for operating remote equipment in response to predetermined signals comprising, tone generator means for continuously producing a plurality of tone signals, push button controlled switching means for selecting a predetermined number of said tone signals, and timing means automatically operated in response to the selection of said predetermined number of tone signals for transmitting said tone signals selected in a particular sequence.

HERBERT C. WATERMAN. MARION R. WINKLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,726,947 Chauveau Sept. 3, 1929 1,765,471 Wensley June 24, 1930 2,147,710 Mallina Feb. 21, 1939 2,232,398 Lundstrom Feb. 18, 1941 

